TITLE: GCN CIRCULAR NUMBER: 13104 SUBJECT: GRB 120323A: Fermi LAT observations DATE: 12/03/25 17:28:31 GMT FROM: Thomas P.H. Tam at Nat.Tsing Hua U. P.H.T. Tam and A.K.H. Kong (NTHU) report: We report on the Fermi/LAT observations of the short (~0.5s) and very bright GRB 120323A that triggered Fermi/GBM (Gruber & Connaughton, GCN 13099), Konus-Wind and a few other detectors (Golenetskii at al., GCN 13102). Using the 10-degree radius data centered on the IPN Triangulation position (GCN 13102), we did not find any significant emission above 60 MeV from this circular region during the prompt emission nor between 0.5 and 100 seconds after the Konus-Wind trigger time (T0). Extrapolating the high-energy photon index, beta, which is 2.9, in the best-fit Band function (GCN 13103) to the LAT energy range, we derived 90% C.L. upper limits (0.1-10 GeV) for the following periods as tabulated below (calculated using Feldman & Cousins, 1998 formulation): Epoch U.L. (ph/cm2-s) T0 to T0+0.5s 3.5e-3 T0+0.5s to T0+1.0s 3.5e-3 T0+1.0s to T0+3.0s 8.7e-4 T0+3.0s to T0+10s 2.5e-5 T0+10s to T0+100s 1.3e-5